Mathematics Problem Solving
Volume 3, Number 18, January 20, 1998
xxxxWhen you average a set of
numbers, it's like saying: If all these numbers were the same
value, this is what each number would be.
xxxxIf you take a few tests and get different scores on each one, your average score is what you would have gotten on each test if all the scores were exactly the same. An average sort of flattens everything out.
xxxxIf Stephanie takes three spelling tests and her scores are 80, 90 and 100, her average is 90. It's as if she got 90, 90 and 90 instead of her actual scores. In both cases the scores are worth 270 points in all.
xxxxThere are just 2 simple steps to calculating an average.
xxxxxxxx1. Add the numbers.
xxxxxxxx2. Divide the sum by how many numbers you added.
xxxxIn the above spelling test example:
xxxxxxxxStep 1: 80 + 90 + 100 = 270
xxxxxxxxStep 2: 270 / 3 = 90 (The symbol / means "divided by".)
xxxxHere's another example:
xxxxTo find the average of 18, 24, 0, and 6: Add 18 plus 24 plus 0 plus 6. You get 48. You added four numbers, so divide 48 by 4. The average is 12.
xxxxSee if you can use the two steps for finding the average to solve the following problems.
1. Daryl has taken two math tests during the current marking period. He got 72 % on the first test and 98 % on the second test. Daryl's test average is _____%.
2. Ryan started reading his new book on Monday. He read 75 pages on Monday, 102 pages on Tuesday, and the remaining 96 pages on Wednesday. Ryan read an average of _____ pages per day.
3. Megan runs every day. She runs 3 miles a day on weekdays (Monday through Friday), and 10 miles a day on weekends (Saturday and Sunday). What is the average number of miles that Megan runs each day?
4. These are the members of the Science Mysteries Club: Jeff - age 11, Christina - age 12, Lisa - age 17, Patrick - age 17, and Sarah - age 13. What is the average age of club members?
In the following problem, the first step has been done for you.
5. Amanda's baseball team scored 18 runs in last night's game. That's an average of _____ runs an inning. (There were nine innings in the game.)
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